In a large scale computing environment, such as one in which one or more storage subsystems are attached to one or more host devices, some computing resources are shared by various components. For example, a storage subsystem may include one or more storage controllers, each having two clusters, each cluster having up to 16 logical storage partitions. A single power controller may be shared among many (or all) of the partitions. The power controller provides power system management for the attached clusters as well as other functions which are common to the clusters and partitions.
Typically, the power controller requires that one of the attached partitions provide processing operations. The conventional process by which a partition is selected is as generally follows. The power controller includes a microcode lock register to store the address or other ID of the selected master partition. At power-on, a reset or other similar event, the contents of the register are initialized to 0. Thereupon, each attached partition attempts to write its respective ID to the lock register. To determine the “winner”, each partition reads back the contents of the register. If a particular partition reads back its own ID, that partition begins to serve as the master while the other partitions continue their normal operations.
Occasionally, a master partition will fail, hang or attempt to relinquish its status as master. There is currently no procedure to establish a new master in such circumstances.